1. Field of the Invention
The present invention relates to a lever-operated hoist for hoisting up or hoisting down by repeatedly turning an operation lever, and more particularly to a lever-operated hoist with an operation lever support structure for smoothly idling in the horizontal state.
2. Description of the Prior Art
A general support structure of an operation lever in a conventional lever-operated hoist is shown in FIG. 7, in which a cover part b of an operation lever a comprises an inside tubular part c, a brake cover e attached to a side plate d of the hoist main body comprises a tubular part f, and the inside tubular part c of the operation lever a is rotatably supported on this tubular part f. The tubular parts c, f are parallel to the axial line of a drive shaft g. In addition, h is a driven wheel, i is a friction plate, j is a brake release spring, k is a driving wheel, and l is a manual operation wheel.
In such support structure, however, since its support surface, that is, the outside surface of the tubular parts c, f is a tubular surface parallel to the axis of the drive shaft g, the support surface can bear the load only in the radial direction. Also, in order to maintain smooth rotary movements of these support surfaces, the diameters of the two support surfaces a different, providing a slight gap between them. Accordingly, the operation lever a is likely to produce an excessive play not only in its original rotating direction (the rotating direction of the drive shaft g), but also in the axial direction of the driving shaft g, and consequently a stable support state is not obtained. As a result, when operating the hoist, the inside tubular part c of the operation lever a often contacts the driving wheel k, or the outside tubular part m at the opposite side of the tubular part c is likely to contact the driving wheel k or manual operation wheel l, and the operation of the hoist is not smooth.
In other words, while idling, that is, in a no-load state without suspending a load, when the manual operation wheel l is operated and the lower hook of the load chain (not shown) is pulled to return the load chain to the specified length, if such contact as mentioned above occurs, the rotating force of the driving parts such as the driven wheel h, driving wheel k and manual operation wheel l mounted on the drive shaft g is increased, and it is not rotated smoothly. Such event is particularly evident when using the hoist in the horizontal state.
In this regard, a support structure as shown in FIG. 8 was proposed. In detail, the inside tubular part c of the operation lever a and the tubular part f of the brake cover e are arcuate, and these tubular parts c, f are fitted so as to be rotatable and not to move in the axial direction of the drive shaft g (for example, Japanese Patent Publication No. 59-163298, Japanese Utility Model Disclosure No. 58-99289 and Japanese Utility Model Publication No. 62-18625).
However, if the tubular parts c, f are arcuate high precision is required in the machining of these fitting parts in order to maintain with precision the assembly of the operation lever a to the brake cover e. As a result, the number of manufacturing steps for the support structure increases, and it takes time and labor in its assembling, and the working efficience becomes poor, and the manufacturing cost is raised.